1. Field of the Invention
The present invention relates to an improved process for the preparation of vinyl-tri-(tertiary-substituted)-alkoxysilanes and, in particular, to a hydrosilation process for producing a high yield of vinyl-tri-(tertiary-alkoxy) silanes of high purity.
2. Description of the Prior Art
The hydrosilation reaction was discovered about 1947 and, over the years, has become one of the best known and most widely practiced reactions in organosilicon chemistry. It enjoys a broad spectrum of large scale commercial applications and has been the subject of thousands of publications and extensive reviews, including the following monographs:
E. Lukevics and M. G. Voronkov, Organic Insertion Reactions of Group II Elements, Consultants Bureau, N.Y., 1966; PA0 C. Eaborn and R. W. Boh, Organometallic Compounds of the Group IV Elements, Dekker, N.Y., 1968, Vol. I; PA0 M. G. Pomerantseva et al, Preparation of Carbafunctional Organosilanes by an Addition Reaction, Moscow, 1971; PA0 E. Lukevics, Russ. Chem Rev., 46, 264 (1977) and PA0 E. Lukevics et al, J. Organometal Chem. Library 5, 1977, pp. 1-179. PA0 HSi[OC(C.sub.2 H.sub.5).sub.3 ].sub.3 ; PA0 HSi[OC(C.sub.3 H.sub.7).sub.3 ].sub.3 ; PA0 HSi[OC(CH.sub.3)(C.sub.4 H.sub.9).sub.2 ].sub.3 ; PA0 HSi[OC(CH.sub.3)(C.sub.3 H.sub.7)(C.sub.4 H.sub.9)].sub.3 ; PA0 HSi[OC(CH.sub.3).sub.3 ].sub.3 ; PA0 HSi[OC(CH.sub.3)(C.sub.2 H.sub.5).sub.2 ].sub.3 ; PA0 HSi[OC(CH.sub.3).sub.2 (C.sub.2 H.sub.5)].sub.3 ; PA0 HSi[OC(C.sub.2 H.sub.5).sub.2 (CH.sub.2 CH.dbd.CH.sub.2)].sub.3 ; ##STR1## HSi[OC(CH.sub.3).sub.2 (C.sub.6 H.sub.5)].sub.3 ; HSi[OC(C.sub.6 H.sub.5).sub.3 ].sub.3 ; ##STR2## HSi(OC(CH.sub.3)(C.sub.2 H.sub.5)(C.sub.12 H.sub.25)].sub.3 ; HSi(OC(CH.sub.3).sub.2 (C.sub.13 H.sub.27)].sub.3 ; PA0 HSi[OC(CH.sub.3).sub.2 (CH.sub.2 CH.dbd.CH.sub.2 CH.dbd.CHCH.sub.3)].sub.3 PA0 HSi[OC(C.sub.2 H.sub.5).sub.2 (CH.sub.3 C.tbd.CH)].sub.3. PA0 tri-t-butoxysilane, tri(2-methyl-2-butoxy)silane and tri(3-methyl-3-pentoxy)silane.
Various classes of platinum compounds have been found to be effective hydrosilation catalysts. Chloroplatinic acid, which is a soluble form of platinum, has proved to be an especially effective hydrosilation catalyst, as disclosed in U.S. Pat. No. 2,823,218 issued Feb. 11, 1958.
In U.S. Pat. No. 2,637,738, issued May 5, 1953 it has been proposed to react triethoxysilane with acetylene in the presence of a platinum black catalyst at temperatures of 130.degree. C. and pressures of 20 atmospheres to form vinyltriethoxysilane. In this reaction yields were said to be relatively low and a substantial quantity of 1,2-bis(triethyoxysilyl)ethane by-product was also produced.
Japanese Pat. No. 57-04996, issued Jan. 11, 1982 discloses that acetylene can be reacted with trialkoxysilanes in the presence of chloroplatinic acid at reaction temperatures less than about 180.degree. C. The major product formed was 1,2-bis(trialkoxysilyl)ethane. With a platinum halide phosphine catalyst, PtX.sub.2 (PPh.sub.3).sub.2, the trialkoxysilanes reacted with acetylene to provide major amounts of vinyltrialkoxysilanes and significant and unacceptable amounts of undesired by-products, such as 2-bis(trialkoxysilyl)ethanes.
The art has recognized to the desirability of providing a process to produce high yields of relatively pure vinyl-tri-(tertiary substituted)alkoxysilanes and, especially, vinyl-tri-(tert-alkoxy)silanes for use as intermediates and reactive coupling agents by hydrosilation techniques. However, the hydrosilation techniques disclosed in the art have not contemplated producing such tertiary alkoxysilanes. In general, the prior art techniques, as they relate to hydrosilation of tri-(primary)-alkoxysilanes and tri-(secondary)-alkoxysilanes, have taught that reaction temperatures should be on the order of less than about 180.degree. C. and that undesired by-products, especially bis(trialkoxysilyl)ethanes, are invariably produced.
As set forth herein the tri-tertiary substituted alkoxysilanes of the invention are referred to as tri-t-alkoxysilanes and the tri-tertiary-alkoxysilanes of the invention are referred to hereafter as tri-t-alkoxysilanes.